It is easy to flatten fibre prints. Let them dry and they will curl in all ways and this is normal. Put them face down on a dry towel and hold the left edge with your fingers. Use a straight edge on the back of the print and pull the print to the left under the straight edge. Most of the curl will have gone. Do it as many times as you need and the print will be almost as flat as a resin coated one. Just right for mounting.

I am having great success in drying fiber papers flat using one of these plant presses.

The fiber papers go in between the blotter papers and the corrugated sheets and I leave them in the press for a week or so. After they come out of the press they are very flat, but over time they regain a slight curl length wise, but I don't have a problem mounting them.

Having recently spent several weeks working on my portfolio, and accidentally ruining a day's worth of work in the flattening process, here is what I now do: heat the dry mount press; place the print face down on a sheet of acid free foam core, with a sheet of release paper on top; heat the print for a minute or two; place print into a sandwich of release paper under a 3/4' piece of MDF to cool. This gets it 90% flat. For 100%, I leave the print in the press, turn it off and let it cool. It comes out flat as a floor.

If you heat the print with the glossy side in contact with the release paper, you will often get a dimple, or the release paper will slightly emboss the glossy finish and ruin it. I was very surprised to find that the foam core does not ruin the coating.

I know I must be missing something here. Why don't you just use clean mat board in your press, again?

I flatten prints in "pockets" of glassine, which is inexpensive, and recommended to me by a museum conservator. I stack up the pockets, so there are two layers between all prints except the top one, then release paper, close the press, turn on, allow to get warm to the touch on the top outside, turn it off, and come back when cool. Very flat, although, as some have said, 3 months later when I take them out to frame, depending on humidity, they can re-curl.

FWIW, since this thread started I enthusiastically tried the brown tape/ glass method, and it certainly makes a very flat print. But I don't much like having to cut off the margins by which I handle the print until it is dry mounted; and I found it pretty tedious having to clean the tape remnants off the glass later. So I have gone back to drying prints face down on plastic mesh screens overnight, then leaving them in a stack under a heavy sheet of glass for a few days. I place a waste print face down on top of the topmost one, and have no sticking problems.

Drain the print or prints, dry on plastic screen. place dried print or prints on top of one another under a piece of glass and set a one gallon jug of water on glass, leave over night. They will be nice and flat, been doing it this way for years, it's easy and cheap.

I am going through various methods of trying to dry fibre prints. Today, I put some prints face down on a plastic screen. I usually put them face up because I am worried that the screen will have a negative effect. When I took them off, a few tiny bits of emulsion stayed on the screen, ruining all the prints. I think it might be because I did not use a hardening fixer. Any thoughts?